Showing papers by "Baohong Hou published in 2012"

Kinetics Study on the Liquid Entrapment and Melt Transport of Static and Falling-Film Melt Crystallization

Abstract: Experiments were carried out to study the kinetics of crystal growth and the sweating process in two kinds of melt crystallization modes: static melt crystallization (SMC) and falling-film melt crystallization (FFMC). The system utilized in this paper was hyperpure phosphoric acid with water and trace amounts of metal ions as impurities. The kinetic experimental data of crystal growth, liquid entrapment, and the melt-transport process were well fitted by power function equations (R 2 > 0.947). The fractal and porous media theories were introduced to improve the model of melt transport and explain the difference between the two modes. The separation efficiencies of SMC and FFMC on different ion impurities were compared. The SMC mode separated calcium and ferrum ions with higher efficiency than the FFMC mode, while the FFMC mode separated sodium and magnesium ions better than the SMC mode. A combined operation mode was suggested to prepare hyperpure phosphoric acid in industrial applications.

Determination of Thermodynamics in Various Solvents and Kinetics of Cefuroxime Sodium during Antisolvent Crystallization

Abstract: This work reports new measurements of solubility of cefuroxime sodium in pure water in the temperature range from (281.15 to 307.75) K and binary liquid mixture as a function of composition at atmospheric pressure. According to the results of solubility of cefuroxime sodium in various solvents, antisolvent crystallization was determined, and acetone was chosen as the antisolvent. Furthermore, the induction time of cefuroxime sodium was measured to deduce the nucleation and growth mechanism. It is found that only homogeneous nucleation occurred at the chosen supersaturation according to the classical nucleation theory equation. It was also speculated that the growth mechanism of cefuroxime sodium follows the diffusion-controlled growth in view of the value of the surface entropy factor.

Coarse crystal layer growth and liquid entrapment study with gradient freeze technology

Abstract: The coarse crystal layer growth and liquid entrapment processes were investigated with gradient freeze technology in this paper. The research system was hemihydrate phosphoric acid (H3PO4·0.5H2O) crystal-phosphoric acid aqueous solution. The distribution coefficients of ions (Ca 2+ ,F e 3+ and Na + ) in this system were measured. The effect of supercooling degree gradient on layer growth and the effect layer growth rate on ions redistribution were studied. The result indicated that the layer growth rate increased with supercooling degree gradient as an exponential curve. The distribution coefficient tended to increase as an approximate ‘S’ curve when coarse crystal layer growth rate increased. The ‘three region’ theory was applied to explain this phenomenon. Each ion’s diffusion parameter was obtained, which contributed to explain the separation differences between different ions. The work in this paper also indicated that layer crystallization was an effective separation technology for electronic grade phosphoric acid preparation.

Method for monitoring solubility, metastable zone and solution concentration on line in crystallization process of organic salt system

Abstract: The invention relates to a method for monitoring solubility, a metastable zone and solution concentration on line in a crystallization process of an organic salt system. The solution temperature of the system can be determined according to the mutational point in an electrical conductivity and temperature relation curve in a heating process, so that the solubility curve of a solute in the solvent is determined. The crystallization temperature of the system can be determined according to the mutational point in an electrical conductivity and temperature relation curve in a cooling process, so that the metastable zone of the solution system at the cooling rate is acquired. Coefficients of recorded electrical conductivity and temperature are calculated by using a least square method according to a relational expression of the electrical conductivity and the solution saturation temperature, so that the relation between the electrical conductivity and the solution concentration is acquired, and the super-saturation degree of the solution to be detected is calculated. The method is applied to measurement of various organic salts in polar organic solvents in the industrial crystallization process under different operating conditions. The method is practical, simple and convenient, can realize on-line measurement, and has the advantages of wide measurement temperature range, wide solution concentration range, simple operating instruments, low cost and strong practicability.

Crystals of carvidilol dihydric phosphate and preparation method thereof

Abstract: The invention relates to crystals of carvidilol dihydric phosphate and a preparation method thereof. Characteristic peaks, at the angle of diffraction of 2Thata degrees, infrared spectrums and TG-DTA, of an X-ray powder diffraction pattern are defined. The preparation method comprises the following steps of: dissolving carvidilol solids into the mixed solvent of alcohols and water to prepare 40 to 60 g/L suspension; heating the suspension to 60 to 80 DEG C until the solids are completely dissolved; adding dropwise the aqueous solution of phosphoric acid into the solution; cooling the mixed solution to 15 to 25 DEG C; adding dropwise a solventing-out agent into the mixed solution, wherein the using amount of the solventing-out agent is 0.35 to 0.65 times the volume ratio of the mixed solvent; and filtering the prepared suspension, and drying the crystal products of the carvidilol dihydric phosphate to a constant weight. The XRD pattern and a stereoscan photograph can prove that the crystallinity of the products is high, the granularity of the crystals is relatively larger, the surface of the crystal is bright and clean, and the rate of filtration is high.

Crystallization preparation method of cloxacillin sodium

Abstract: The invention discloses a crystallization preparation method of cloxacillin sodium. The method is as follows: stirring added 0.03g/mL-0.2g/mL sodium isooctoate-alcohol solution in 0.1-0.2g/mL cloxacillin acid solution at the temperature of 5-25 DEG C, reacting and crystallizing, wherein the pH value of the final point of the reaction process is 5.5-7.5; then adding an ester or ether solventing-out agent in the solution for solventing-out crystallization, wherein the volume of the ester or ether solventing-out agent is 7-11 times that of cloxacillin acid solution; and carrying out centrifugal separation, solvent washing and drying on crystal slurry after crystallization, so that the cloxacillin sodium product is obtained. The crystal habit of the product is of a flaky shape, the particle size is large, the residue of the solvent is obviously improved, the crystal slurry is easy to filter, wash and dry, and the production period is greatly shortened. The high-performance liquid chromatography (HPLC) content of the product is above 99.4%, and the pH value is 5.7-6.0, thereby achieving the requirement of China Pharmacopeia 2010. The molar yield in the crystallization process is more than 88%.

Novel crystal form of cefuroxime acid and preparation method thereof

Abstract: The invention relates to a novel crystal form of cefuroxime acid and a preparation method thereof. In X ray powder diffraction, the novel crystal form of cefuroxime acid has characteristic peaks at diffraction angles 2 theta of 8.06, 9.96, 10.44, 11.84, 12.82, 16.34, 19.02, 20.02, 21.86, 23.22, 25.46, 25.98, 33.12, 34.24 and 36.40 degrees. The preparation method comprises the following steps of adding cefuroxime raw materials into an acetonitrile mixed solvent to obtain a solution having a concentration of 0.1 to 0.2g/ml, stirring at a temperature of 25 to 35 DEG C for complete dissolution, continuously stirring for 30 to 60 minutes, carrying out filtration and decoloration, transferring filtrate to a crystallizer, adding a hydrochloric acid solution into the crystallizer to adjust a pH value of the mixed solution to 3-4, cooling to a temperature of 10 to 15 DEG C, adding cefuroxime acid seed crystals into the crystallizer, carrying out crystallization for 1 to 2 hours, adding water as a solventing-out agent into the crystallizer, sequentially cooling to a temperature of 0 to 5 DEG C, carrying out crystallization for 1 to 3 hours, filtering, washing filter cake by a washing solvent, and drying to obtain products. The novel crystal form of cefuroxime acid has HPLC content above 99.3%, avoids crystal accumulation, has large particle sizes, wherein a main particle size is more than 100 microns, and also has uniform particle size distribution and a single-cycle mole yield above 88% in crystallization.

Method utilizing coupling reaction crystallization to prepare cefuroxime sodium

Abstract: The invention relates to a method utilizing coupling reaction crystallization to prepare cefuroxime sodium, which comprises dissolving cefuroxime acid in a mixed solvent at 20-30 DEG C to prepare a solution with the concentration to be 0.025g/ML-0.1g/Ml; adding an alkaline sodium salt water solution into the solution; mixing for 10-20min at constant temperature to enable a reaction to be complete, and adding cefuroxime sodium seed crystal; adding an elution agent after 10-20min; cooling the temperature of the solution to 0-5 DEG C, and keeping at the constant temperature for 0.5-2h; filtering, washing and drying the obtained suspension, and obtaining a cefuroxime sodium product. The method reduces the adsorption filtration process of activated carbon and avoids loss of yield. The method achieves coupling of reactions and crystallization, and the methods of elution crystallization and cooling crystallization are combined with each other in the crystallization process, the crystallization process is controlled easily, the particle size of the product is uniform, the liquidity is greatly improved, the purity is higher than 99.5%, and the yield is over 92%.